# TODO 字符串大小写转换
st4 = 'HeLLo World'
str5 = st4[0].lower() + st4[1:6]+st4[6].lower() +st4[7:]
print(str5)

st1 = 'hello world'
print(st1.capitalize())
print(st1.title())

str2 = 'HELLO WORLD'
print(str2.lower())
print(str2.upper())

str3= 'heLLO world'
print(str3.swapcase())
